1. Field of the Invention:
This invention relates to an automatic focus control system and more particularly to an automatic focus control system including an active type automatic focusing device which automatically adjusts the focal point of an optical system by projecting a signal on an object and receiving a resultant reflected signal; and also to a camera using this focus control system.
2. Description of the Prior Art:
There have been proposed active type automatic focusing devices of various kinds. It is known that still picture cameras, 8 mm motion picture cameras, video cameras, etc. are using such active type automatic focusing devices. However, the various kinds of conventional active type focusing devices consume an extremely large amount of power. Because, in order to secure a sufficiently high degree of performance, they require a high output for signal projection whether or not the signal to be projected on an object is a light or an ultrasonic wave. Although high output infrared ray emitting diodes (IRED) and the like have recently been developed, their power consumption still remains large. This is a serious problem especially for motion picture cameras, portable video cameras and the like which must have an automatic focusing device constantly operative during photography. When using portable video cameras in particular, the importance of portability increases and, accordingly, their power source capacity is further limited. Therefore, great power consumption by the above active type focusing devices is becoming more serious.
It is an object of the present invention to provide a novel automatic focus control system which eliminates the above prior art shortcoming.
It is another object of the invention to provide a novel automatic focus control system capable of greatly reducing power consumption, although the system includes an atuomatic focusing device of the active type which intrinsically causes large power consumption.
It is a further object of the invention to provide an advantageous automatic focus control system which is capable of greatly reducing power consumption by a rational method of actuating a focusing device only when necessary.
Another object of the invention is to provide a camera advantageously using the above novel automatic focus control system.
Still another object of the invention is to provide an advantageous video camera or a TV camera using the above novel automatic focus control system.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.